Locknivar Boiler Problem

I have a locknivar boiler (model # RBN090) that is not working properly. The thermostat calls for heat, the boiler relay clicks on, the gas ignites and then it only stays on for about 30 seconds to a minute then turns off. This cycle repeats without every really getting up to the proper temp. Any ideas on what this can be? The air damper seems to be opening and the gas ignites so I am guessing some type of thermostat setting or some sensor not working properly. Any help before the cold temps set in would be very helpful. Thanks!

The manual, or somewhere inside the unit, will be a wiring diagram; the manual will have a troubleshooting guide. If you don't have one, you may find one on the manufacturer's website.

One of the interlocks or sensors may need to be cleaned or replaced. It sounds like the flame sensor is not detecting the burner is coming on. This could be dirty, misaligned, or not working. The leads could be corroded or loose. Lots of possibilities.

If the circulator pump is not turning on, the water inside the heat exchanger could be getting too hot, and that's shutting it down. Depending on where your temperature gauges are, you may or may not be able to see that.